Bistable displays that do not require continuous voltage application to maintain their state are becoming particularly important in low power applications. Various technologies can be utilized to provide bistable displays, including, but not limited to: Cholesteric Liquid Crystal Displays (ChLCD); Electrophoretic Displays; Bi-Stable STN Displays; Bi-Stable TN Displays; Zenithal Bi-Stable Displays; Bi-Stable Ferroelectric Displays (FLCD); Anti-Ferroelectric Displays; Interferometric Modulator Display (IMoD); and Gyricon displays (oil-filled cavity, beads are “bichromal,” and charged).
In particular, bistable reflective cholesteric liquid crystals (ChLCs) have been of great interest in the last several years because of their excellent optical properties and low power advantage. Two major ChLC drive schemes are known to be available at this time: (1) conventional drive and (2) dynamic drive. Typically, ChLC displays (ChLCDs) require drive voltages around 40V. High multiplex, off-the shelf (OTS) STN-LCD drivers can accommodate this requirement for a conventional drive. However, off-the-shelf drivers for commercial dynamic drive ChLCDs would be beneficial.
Further, the development of purely reflective display technologies enables a very power efficient display module in that backlighting of the display is not necessary. However, this type of system is severely challenged in achieving full color. Typical display technologies achieve full color imaging through the use of individual red, green and blue (RGB) pixels that are typically patterned side-by-side rather than on top of one another. Resulting color images are obtained by allowing light through the appropriate pixels.
For example, if the RGB sub-pixel sizes are about equal, a purely red image will be created by turning on the red sub-pixels, and turning the green and blue sub-pixels off. Purely blue and green colors are likely generated by activating only those color pixels. Other colors are generated by using combinations of the primary pixel colors in various shades, for example.
However, the above implementation can result in very poor performance when applied to purely reflective technologies such as Cholesteric LCDs (ChLCDs). In such cases, the amount of light reflected from the desired color may not be of sufficient intensity to overcome the effects of the neighboring pixels that are not reflecting. These types of reflective systems can result in total reflectivity of around ⅔ less than a single pixel of comparable size as the three RGB pixel, because the amount of surface area available for reflecting light is reduced by dividing the pixel area into sub-pixels. This may result in images that are below desirable contrast and brightness levels.
In addition, it can be physically challenging to accommodate the packaging and interconnects of the three sets of drive electronics to the LCD. Modern display drive electronics have evolved to offer dual-mode drive electronics, i.e., display drivers that can function as both a row driver and a column driver depending upon mode configuration. However, previously a single driver IC could not perform both row and column functionality at one time.
Examples of color imparting layers are provided in U.S. Pat. No. 5,493,430, entitled “Color, Reflective Liquid Crystal Displays,” which is incorporated herein by reference in its entirety. Application Ser. No. 09/329,587, filed on Jun. 10, 1999 entitled “Stacked Color Liquid Crystal Display Device,” is also incorporated herein by reference in its entirety.
Co-pending application Ser. No. 10/782,461, filed on Feb. 19, 2004 incorporated herein by reference, discloses a configurable driver IC that can utilize a single IC to drive both row and column electrodes concurrently, or that can be cascaded with additional driver ICs to provide a flexible display driver solution. It would be useful to provide a display that can utilize such a driver to simplify the driving scheme.